The Taste of Climate Change – 25 Magazine: Issue 4

The Taste of Climate Change – 25 Magazine: Issue 4

TThere are many memorable cups of tea. For me, the most memorable cups are those that change the way we look at the world, the cups that spur action and shape the direction of what we do. It has been more than a decade since a cup of green Pu-erh drove my research journey to examine the effects of climate change on tea quality.

SELENA AHMED offers sustainability lessons from farmers of tea agroforests in Issue 4, 25 Magazine.

It was the late spring of 2007. I was in an Akha village in the Bulang Mountains of Yunnan Province of southwestern China, carrying out fieldwork for my doctoral studies on the ecology and culture of tea. Southern Yunnan and the adjacent montane areas of Myanmar, Laos, Vietnam, and India are the motherland of the tea plant (Camellia sinensis), the source of all green, white, black, oolong, and Pu-erh tea. The mountains of southern Yunnan are the epicenter of diversity for tea.

I had spent the day measuring plant biodiversity in the community’s tea agroforests. While wandering through these agroforests, it is sometimes difficult to decipher the managed tea systems from the forests that buffer them. Ancient tea plants dripping with orchids and covered in moss flourish in these shady agroforests, reaching heights of up to 15 meters tall. Tea grows side by side with other trees locally used for food, medicine, construction material, dye, fodder, fuelwood, ritual, and tools. The tea plants themselves seem to vary from one to the next in every way – different sizes, ages, and cultivars. In fact, a hectare of agroforest managed by an Akha smallholder family may be home to up to 15 different cultivars of tea.

I packed up my plant press and other research tools as the early evening glow set in and headed to Li Gan and Aye Ying’s house for a cup of tea. This had become a frequent ritual after a day of fieldwork. Aye Ying would brew a cup of the freshest harvest that she had pan roasted. After drinking a mouthful of green Pu-erh, she noted with confidence, “It has changed. The taste has changed.” It had been just a few days previously that I shared tea with these tea farmers on their porch overlooking the remarkable tea agroforests beyond the village settlement. That was the dry season, and the East Asia monsoon had since arrived. Aye Ying was referring to the flavor changes in tea brought about by the advent of the monsoon.

Spring tea in Yunnan fetches the highest price of the three harvest seasons because it is associated with the most complex, intense, yet balanced flavor profile, characterized by a strong floral, citrus, and woody aroma, and a bittersweet taste with a sweet lingering after taste at the back of the throat, referred to as gaan. Tea’s medicinal and stimulant attributes are also perceived to be stronger for the dry spring harvest.

As soon as the monsoon hits, tea in southern Yunnan is classified as monsoon tea with a less-intense tasting infusion compared to spring tea. Sensory perceptions of tea farmers and tea traders dictate when this shift occurs, with price signals and flavor shifts that reverberate through the entire supply chain, and back to influence farmer income as well as the way farmers manage their tea gardens. Tea farmers are concerned with these sensory changes because monsoon tea fetches only half the price of spring tea. In the past few decades, tea farmers have observed that the monsoon season is getting longer due to climate change, including more intense and unpredictable rains.


Li Gan explained that while the variability in precipitation is the biggest climate driver to influence tea quality in their tea gardens, this is not the only change that people, plants, and ecosystems are experiencing. In addition to climate change, this tea community is also experiencing tremendous change from an expanding tea market, globalization, political and lifestyle changes, deforestation, and more. All of these changes are impacting the culture and ecology of tea.

As regards climate change, Li Gan and Aye Ying have also observed that temperatures have increased during their lifetime leading to fewer cold days, warmer winters, warmer summers, and less frequent occurrence of frost. The changes in precipitation and temperature impact both tea quality and yields, sometimes with an inverse relationship. Li Gan went on to share that the spring harvest season is also starting earlier but the early tea bud burst is regarded to disrupt flavor development processes during plant dormancy as well as heighten the vulnerability of young leaves to frost damage.

Aye Ying brewed another cup of tea from leaves harvested from a relatively new tea garden, cultivated as a monoculture open-sun tea garden grown from clonal propagules, where tea plants are uniformly pruned into shrubs. “This tea has really changed. We should try processing it differently, maybe a black tea instead of Pu-erh,” she ventured. Monoculture-style tea gardens were introduced to the village by the Chinese Government as part of the Grain for Green program and provide farmers with subsidies. Many farmers in Yunnan have replaced their traditional tea agroforests with these monoculture-style gardens. These systems require agrochemical input including fertilizers, herbicides, and pesticides unlike the community’s agroforests that rely on a diversified forest-like structure to provide ecosystem services of fertility and pest control. However, numerous farmers in this Akha village continue to manage tea agroforests because of the higher quality tea and because these systems are tied to their cultural identity.

Li Gan revealed that tea from their agroforests is more resilient to overall climate variability and unpredictability compared to tea from their monoculture tea gardens. He explained that this is partially because tea plants cultivated from seeds rather than from clonal propagules are more resilient to climate variability. Tea plants managed as trees rather than pruned into shrubs are also more resilient to climate extremes. Aye Ying added that this is another reason why they are mindful of maintaining canopy coverage in their tea agroforests as well as forested buffers.

It was this cup of tea over a decade ago that introduced me to not only the vulnerability of tea systems to climate change, from the plants through the whole supply chain, but also of the power of human management and processing in actively responding to climate change. The experience drove my research agenda – tea farmers provided me with research observations and hypotheses to test. Frequent reports in the news since 2010 highlight that climate change is also impacting tea systems in tea producing countries around the world – including India, Kenya, and Sri Lanka – resulting in severe and irreversible impacts on tea production and associated livelihoods. I have since gone on to initiate a collaborative tea project with an interdisciplinary team of scientists and industry partners to quantitatively measure how climate change is impacting tea quality, using state-of-the-art techniques. Tea plants provide a compelling system to understand climate change, as they are cultivated in production systems for numerous decades and thus experience the multiple decadal effects of climate change.

Field Research

Our interdisciplinary team has been carrying out research on tea and climate change across agroclimatic zones in major tea producing regions in China since 2012. Drawing from the seasonal variability that farmers are experiencing, we have been carrying out in-field experiments across different seasons coupled with manipulative greenhouse experiments as proxies for understanding long-term climate change. A snapshot of one field season shows that tea growth during the monsoon onset period in southwestern Yunnan was up to 50% higher compared to the spring drought. Bringing back to the lab tea samples that were collected before and during the onset of the monsoon, I found the amounts of catechin and methylxanthine secondary metabolites – major compounds that determine tea quality, including flavor – were up to 50% lower during the monsoon onset while total phenolic concentrations and antioxidant activity increased. While the inverse relationship between tea growth and concentrations of individual secondary metabolites suggests a dilution effect of precipitation on tea quality, the increase in total phenolic concentrations and antioxidant activity suggests additional plant stress responses.

My collaborators in the lab of Albert Robbat at Tufts University in Massachusetts, US further analyzed these samples for their aromatic profiles and found that the spring tea from Yunnan had a slightly greater number of aromatic compounds (201) compared to the monsoon tea (196) with a total of 59 seasonally unique compounds. Some of these aroma compounds are associated with desirable flavor attributes, while others are associated with less desirable flavor attributes. Within each family of aromatic compounds, metabolite concentrations increased, decreased, or stayed the same following the onset of the monsoon, pointing to the complex impacts of climate variability on tea quality.

The changes we have measured in the amounts of tea secondary metabolites correspond to the sensory perceptions of farmer, consumer, and standardized taste panelists during our taste tests. We also documented a decline of up to 50% in household income from tea sales with the onset of the monsoon and precipitation variability. Hundreds of interviews with tea farmers in Yunnan regarding climate patterns and their effects on tea yields and quality show consensus with the observations of Aye Ying and Li Gan. However, these observations vary with agroclimatic region. While precipitation is the major climate driver of tea quality in southern Yunnan, temperature is the major climate driver of tea quality in eastern China, pointing to the importance of geography in understanding the impact of climate change on tea.

It is also critical to highlight that tea is not the only species in the tea garden that is shifting with climate. All species are vulnerable to climate change, resulting in a cascade of effects with shifting dynamics between species and abiotic and biotic stressors. Some of these interactions can cancel out the effects of climate change, while others can amplify these effects. For example, in a manipulative greenhouse experiment that I led, we found that increased water availability (that parallels extreme precipitation events that are anticipated to become more frequent in the tea producing area of Yunnan) resulted in significantly lower concentrations of a key tea quality compound, epicatechin-3-gallate, while the interactive effects of water with simulated pest pressures canceled out the effects of water alone.

While our interdisciplinary team is still in the process of synthesizing our findings from experiments over the last six years, it has become clear that tea quality is directly impacted by shifts in precipitation and water availability, temperature, greenhouse gases, ultraviolet radiation, and shifting pest pressures associated with climate change. Extrapolating findings from our long-term seasonal and greenhouse studies to long-term climate scenario projections suggests that farmers and consumers face variable implications with forecasted climate scenarios. Our findings further highlight the need for research on management practices to facilitate climate adaptation for sustainable tea production. Luckily, we can start by learning from farmers of tea agroforests.

SELENA AHMED is Assistant Professor, Sustainable Food Systems and Principal Investigator at The Food and Health Lab in Montana State University in the US.

Bulang women from Mang Jing village picking tea in a forest tea garden, on Jingmai Mountain, western Xishuangbanna, Yunnan, China.
10 Tips from Tea Farmers

01 Recognize linkages between environmental, agricultural, and human health. Our interaction with the environment is a key factor in attaining crops that are delicious and support food security and human health.

02 Manage for diversity through the food supply chain. At the agricultural level, this includes managing for biodiversity at the landscape, species, and genetic levels above and below the soil. Agricultural diversification is a promising strategy for climate resilience. Biodiversity should be enhanced in the market sector through diversified product offerings and market strategies to consumers from diverse demographics.

03 Mimic natural ecosystems in managing agricultural systems for multiple ecosystem services. Natural ecosystems provide crucial ecosystem services that support high quality crops including regulating soil nutrients, water quality, and climate regulation. Relying on ecosystem services in agricultural systems rather than agrochemical inputs also helps minimize chemical pollution of soil and water during food production.

04  Cultivate crops for high quality rather than yields and work towards promoting synergies between human and environmental health. It is important to realize that food quality is a multi-dimensional parameter that includes flavor, health attributes, and the resilience of crops to climate variability.

05  Don’t “pamper” crops with agrochemicals. Ecological stress in agricultural systems influences the presence and concentration of secondary metabolites and nutrients in crops that determine flavor and health attributes. Plants produce secondary metabolites as a defense response to stress in their environment. Producing secondary metabolites represents an energetic cost for plants. When plants are overly pampered with pesticides and herbicides, they lose some of their ecological cue to produce many of the secondary metabolites that we value in our cup of tea and coffee.

06 Manage your agricultural systems and food enterprises for the long-term and worst-case scenarios. Expect the unexpected. Realize that systems and connections within and between systems are always changing – you have to keep moving just to stay in the same place with climate change. Don’t put all your seeds in one basket. And most importantly, focus on creating food systems for your great-grandchildren. The resources we have today have been stewarded by generations past. Plant fruit trees you may never harvest, and shade trees whose foliage crowns you may never enjoy.

07 Continuously experiment with innovation in production, processing, and marketing.

08 Share and exchange knowledge, crop germplasm, and skills through developing norms of cooperation. A great rising tide will lift all boats; work together to create big waves. Friendly competition and information-sharing and -exchange among tea growers and supply chain members will result in synergy and progressive ideation that will lead to a more resilient world.

09 Manage for context specificity and interacting effects. What works today may not work tomorrow. What grows well here may not grow well over there. What tastes delicious to me may not taste so good to you. And remember, always try to take a systems approach to see all the connections and interactions. For example, when managing for rainfall in agricultural systems, it will not only be the crops impacted but also the pollinators and microbes and all of their dynamics with plants, the environment, and each other.

10 Support the rights of workers and farming households while fostering direct connections between farmers, enterprises, and consumers to ensure transparency and trust through the food supply chain.

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